The agent is the person or thing that performs the action and is the subject of the active sentence. In most passive sentences, the agent is not mentioned.
Slide 5 - Slide
When do we use a passive?
Agent is unkown
Agent is irrelevant
Agent is obvious
Don't want to say who agent is
Many solar panels are being installed nowadays.
At the end of the service the churchgoers were given the blessing.
Over past months a lot of drug chemicals have been dumped in the countryside.
The lights were left on again all night. Please remember to switch them off.